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Single TTL input to bus CAN interface

Ricard Silvestre71627
Prodigy 20 points
Other Parts Discussed in Thread: SN65HVD234, SN65HVD255

Hello,

I would like to implement a bus can formed by a ring of 20 nodes. Each node should formed by a sensor and a minimal interface to convert a TTL input (sensor output) to the can bus.  Ideally this interface should be formed by :

1 digital input (sensor output)

5 digital inputs  OR an analog input , in order to configure the sensor ID

1 bus can output

1 bus can transceiver

I have been searching on the texas product line but I have not found any device that match with that purpose without a huge quantity of extra features ( extra cost ). I was wondering if some of you have ever posed this kind of application and how he/she has aborded it. Maybe I'm not looking at the right interface, let me know if you have some suggestion.

Thanks a lot beforehand

  • 0
    TI__Mastermind 20590 points

    CAN is a high level protocol.  You cannot simply take a few TTL inputs and make them "talk" CAN.  It would require a fairly large state machine to get the inputs into the CAN protocol with enough over head to then do something with the information.  Generally this application requires a small MCU which would be used to connect the sensors and inputs and then the CAN protocol s/w will run on top to map these sensors to the correct CAN Message IDs and allow the flexibility needed at the system level to adpat it.  A simple CAN transceiver for this would be the following depending on the supply voltages available:  SN65HVD255 (5V supply) or the SN65HVD234 (3.3V supply).  The Stellaris family of MCUs have several with CAN controllers and reference s/w such as the LM4F120:   http://www.ti.com/lsds/ti/microcontroller/arm_stellaris/overview.page?DCMP=Luminary&HQS=Other+OT+stellaris,   http://www.ti.com/tool/ek-lm4f120xl .   The LM4F120 Launch pad could be easily interefaced to the SN65HVD255 CAN EVM to build up one of these simple systems.

    Another good resource is www.ti.com/can

    -- Scott